This invention relates to testing valve assemblies, and more particularly to detecting flow in a backflow preventer assembly.
Backflow preventer assemblies are typically used to restrict backflow into a water supply line. After installation, the assembly is tested for proper operation. The tests are typically performed manually at times when there is access to the assembly and the ability to turn off the water supply.
According to the invention, a method of determining flow through a valve includes determining a first differential pressure across the valve. The valve is then bypassed and a second differential pressure is determined across the valve. A flow decision is determined for the valve based on comparison of the first and second differential pressures.
Embodiments of this aspect of the invention may include one or more of the following features. The method includes determining whether flow is forward, backward, or no flow. If the first differential pressure is within a predetermined positive range and the second differential pressure is substantially unchanged from the first differential pressure, the flow decision is forward flow. If the first differential pressure is substantially non-zero and the second differential pressure is substantially zero, the flow decision is no flow. If the first differential pressure is within a predetermined negative range and the second differential pressure is substantially unchanged from the first differential pressure, the flow decision is backward flow.
The method is performed in an automated fashion from a remote location. The flow decision is determined without input from a flow meter. The first and second differential pressures are determined to within a range, e.g., values greater than a predetermined positive threshold.
The method includes collecting additional data and basing the determined flow decision on the additional collected data as well as on comparison of the first and second differential pressures. Collecting additional data includes determining a first differential pressure for a second valve, bypassing the second valve, and determining a second differential for the second valve. Additional data is collected after the flow decision is determined. If the flow decision is no flow, collecting additional data includes performing a relief valve actuation test. Performing the relief valve actuation test includes opening a vent in a zone of a reduced pressure backflow preventer assembly. The zone includes a relief valve.
A pass/fail decision is determined for the valve based on a comparison of at least one of the two differential pressures to a predetermined value. The method includes stopping the bypassing, and determining the second differential pressure after the bypassing is stopped. The method is performed repeatedly. The method is performed for a check valve in a backflow preventer assembly. The method is performed for a first and a second check valve in a reduced pressure backflow preventer assembly, and the method determines whether a relief valve is discharging based on the first and second differential pressures across each of the two check valves.
Determining the flow decision for the valve includes determining whether there is a backflow through the valve. A differential pressure is determined across a downstream valve prior to determining the first differential pressure across the upstream valve, and a backflow decision is determined for the downstream valve. The backflow decision for the downstream valve is determined prior to any explicit determination of whether there is a backflow through the upstream valve and, thus, implicitly determines whether there is a backflow through the upstream valve.
According to another aspect of the invention, a computer program for determining flow through a valve resides on a computer-readable medium. The computer program includes instructions for causing a computer to determine a first differential pressure across the valve, to bypass the valve, to determine a second differential pressure across the valve, and to determine a flow decision for the valve based on comparison of the first and second differential pressures.
According to another aspect of the invention, an apparatus for determining flow through a valve within a housing, the valve defining an upstream side and a downstream side, includes one or more pressure indicators coupled to the downstream side and the upstream side of the valve, and a bypass coupled to the upstream side and to the downstream side of the valve. The apparatus further includes a programmable device coupled to the one or more pressure indicators and to the bypass. The programmable device is programmed to determine a first differential pressure across the valve, to bypass the valve, to determine a second differential pressure across the valve, and to determine a flow decision for the valve based on comparison of the first and second differential pressures.
According to another aspect of the invention, an apparatus for determining flow through a valve includes means for determining a first differential pressure across the valve, means for bypassing the valve after determining the first differential pressure, means for determining, after bypassing the valve, a second differential pressure across the valve, and means for producing a flow decision for the valve based on comparison of the first and second differential pressures.
According to another aspect of the invention, a method of testing a relief valve in a reduced pressure backflow preventer assembly including an upstream check valve, a downstream check valve, and a relief valve includes determining during a no flow condition a first differential pressure across the upstream check valve, bypassing the upstream check valve after determining the first differential pressure, thereby allowing flow between an upstream side of the valve assembly and a zone between the valves to open the relief valve, and opening a vent to reduce pressure in the zone. The relief valve and the vent are coupled to the zone.
Embodiments of this aspect of the invention may include one or more of the following features. The method is performed in an automated fashion from a remote location. The method includes determining that there is a no flow condition through the upstream check valve, closing the vent, and determining a second differential pressure across the upstream check valve. The relief valve includes the vent and is opened by a control signal.
According to another aspect of the invention, a method of determining flow through a valve includes determining a first differential pressure and a second differential pressure across the valve. A flow decision is determined for the valve based on comparison of the first and second differential pressures.
At least one method and apparatus described can be used, for example, to remotely test a valve, including testing for a no flow condition, a backflow condition, and a forward flow condition. These tests can be performed using hydraulic information such as pressure and without the use of a flow meter or other flow-sensing device.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and implementations will be apparent from the description and the drawings, and from the claims.